In the production of a substrate with patterned ITO, the substrate is adhered to a temporary carrier in order to protect one surface of the substrate, and then is subjected to multiple processing steps including the deposition of ITO at high temperature. After the patterned ITO substrate is fabricated, it needs to be separated from the temporary carrier. Therefore, it is required that the adhesive used in the above process can stand the high temperature in the process, can be thoroughly eliminated from the substrate, and does not contaminate the substrate resulting in adverse influence in the following processing. The patterned ITO substrate obtained from the invention can be used in display devices such as touch panel application.
Polysiloxane-based adhesives are commonly used for temporarily bonding the substrate with the temporary carrier in the art. However, one problem of such polysiloxane-based adhesives is that the unadhered upper surface of the substrate is contaminated by the volatile components or weigh-losing components of the polysiloxane-based adhesives generated at the high temperature processing, rendering great difficulty of applying photoresist thereon in the following step. Even though various solvents are used to clean the unadhered upper surface, still there is polysiloxane residue left on the substrate, resulting in poor spreading of special chemicals, such as optical adhesive and photoresist, on the upper surface of the substrate.
U.S. Pat. No. 5,190,818 discloses an adhesive composition for temporary adhesive bonding of paper sheets, which achieves the temporary adhesive bonding by pressing, and the bonded sheets can be separated later by an appropriate peeling force. The disclosed peelable adhesive composition comprises, as a mixture: (a) an aqueous emulsion or latex of rubber; (b) particles of silica gel; and (c) starch. Said adhesive composition optionally contains other additives. The bonding of the adhesive composition disclosed in U.S. Pat. No. 5,190,818 is achieved by pressing at ambient temperature, and the bonding strength is not very high.
U.S. Pat. No. 5,256,717 discloses a hot melt adhesive composition comprising: a) about 5 to 50% by weight of a polymer selected from the group consisting of: i) an isotatic thermoplastic polybutene-1/ethylene copolymer containing from about 5.5 to 10% by weight ethylene, and ii) low density polyethylene; b) from about 3 to 65% by weight of a solid benzoate plasticizer; c) from about 10 to 90% by weight of a tackifier; and d) from about 0 to 2% by weight of an antioxidant. The curing of the hot melt adhesive composition disclosed in U.S. Pat. No. 5,256,717 is achieved by cooling, and the disclosed composition is in liquid state at high temperature, for example, higher than 150° C. Therefore, the hot melt adhesive composition disclosed in this document can not provide a stable bond at high temperature.
U.S. Pat. No. 6,325,885 B1 provides a temporary pressure-sensitive adhesive providing a temporary bond between an article and a horizontal surface. Said pressure-sensitive adhesive is based on polyorganosiloxane gum.
US 2010/0148160 A1 discloses a laminating adhesive, which can be used and processed at room temperature, comprising: a reactive liquid oligomer and/or polymer; a liquid monomer reactive with the liquid oligomer and/or polymer; and an initiator. Furthermore, US 2010/0148160 A1 discloses the use and the processing of the laminating adhesive at room temperature, particularly, at a temperature no higher than 65° C.
Therefore, there still is the need to find a photocurable adhesive composition capable of temporarily bonding the substrate and the carrier at high temperature, achieving a stable bond there between, and causing no contamination on the substrate.